Conventionally, epoxy resins have been widely used in many ways for encapsulation of an LED element (for example, Japanese Patent Laid-Open No. Hei 11-302499). However, in an LED device with high brightness which is in need of an application to general illuminations, a material for encapsulation of a photosemiconductor element having light fastness (for example, brightness-maintaining percentage) in order to meet the need of high brightness, and transparency (for example, light transmittance), while having heat resistance in order to meet the need of an increase in an amount of heat generated upon lighting-up is desired.